When electrical work needs to be performed on an electrical system in a building or facility, it is typically necessary to trace and identify which circuit interrupter device (i.e., circuit breaker or fuse) is supplying power to a specific AC power branch circuit.
Manual identification of the fuse or circuit breaker can be accomplished by removing each fuse or opening each circuit breaker, thereby disrupting the power flow through the circuit. Each test point must subsequently be examined to determine whether the power to the test point has been disconnected. This method is not only time consuming, but also may not be feasible in situations where it would be hazardous to interrupt the power flow to certain branch circuit outlets, i.e., in a hospital or in environments where there are computers in use without backup power.
Accordingly, there is a need to provide a circuit tester that provides an identification signal that is easily detectable by an adequately sensitive receiver, and is simple to implement and inexpensive to produce.
Accordingly, there is also a need for a circuit tester that provides more reliable identification of a selected circuit branch while making it easier and less time consuming for the user to operate by eliminating the need for manual calibration and the associated potential for user error.
In addition to the need to locate circuit interrupters, there is also a desire to test circuit interrupters. Effective Jan. 1, 2002, the National Electrical code has required that arc fault circuit interrupters (AFCIs) must be installed on electrical circuits that provide household power to bedrooms in new residential construction. This requirement resulted in part from studies conducted under the sponsorship of the U.S. Consumer Product Safety Commission. Electrical and fire safety experts concluded that many household fires are not prevented by conventional circuit interrupters, which detect sustained circuit overloads exceeding the nominal current rating of the circuit interrupter (e.g., 20 amperes) for several seconds or more. A significant number of fires are caused not by sustained short circuits, but by arc faults. An arc fault is characterized, for purposes of this disclosure, by an intermittent arc or sputtering current drawn between hot and neutral electrical leads or between exposed portions of a wire having worn insulation. Arc faults are caused by a variety of circumstances. Although the arc fault may not draw enough continuous current to trip a conventional electromagnetic circuit interrupter, it can still cause-enough localized heat to ignite surrounding flammable substances and cause a fire.
Underwriters Laboratories has published UL Standard 1699, which establishes standards for AFCIs, which are circuit interrupters that can detect arc faults. The UL standard includes test procedures for use by UL and AFCI manufacturers for to test an AFCI. In accordance with the standards, a UL-recognized AFCI is required to provide a test button that a user can press to test the AFCI. When the user actuates the test button, circuitry within the AFCI injects a test signal into the AFCI's arc fault detection circuitry. If the AFCI is operating properly, the AFCI should detect the test signal and the circuit interrupter should trip.
Thus, a user can actuate the test button, which is built into an AFCI, to test the AFCI's functionality. However, to conduct such a test the user must go to the circuit breaker panel, which is often in an inconvenient location. For example, the circuit breaker panel may be in the basement of a house, while the protected circuits are in an upper-story bedroom. Further, without additional equipment, it is typically not easy to determine that a given receptacle in a bedroom is actually connected to the circuit that is protected by the AFCI. Electrical inspectors, electricians, and other users who check AFCIs and their associated circuits could benefit from a device that plugs into an electrical receptacle (e.g., in a bedroom) and quickly identifies whether that circuit is protected by a properly functioning AFCI. It would be further beneficial if the AFCI tester device would be implemented together with a circuit interrupter locator within a same device.
These and other useful aspects of the invention will be apparent to those of ordinary skill in the art having the present drawings, specification and claims before them.